1. Technical Field
The present invention relates to a paper supply apparatus used for automatically transporting paper, and an image forming apparatus and an image reading apparatus provided with such a paper supply apparatus.
2. Related Art
Generally speaking, image forming apparatuses such as printers and image reading apparatuses such as scanners are provided with paper supply apparatuses that supply paper from a placement surface of a paper supply tray to an image forming unit or an image reading unit, and such paper supply apparatuses include paper supply rollers that are rotationally driven while making contact with the paper in order to automatically supply the paper placed on the placement surface.
Furthermore, generally speaking, paper supply apparatuses provided with edge guides that guide the transport of the paper by making contact with the side ends of the paper in the widthwise direction, where the edge guides are configured of a fixed guide and a movable guide so as to enable the guidance of a variety of sizes of paper to be transported, are known.
Meanwhile, a paper supply apparatus in which a paper supply roller is disposed so as to abut the surface of paper on the side of the fixed guide has been disclosed (for example, see JP-A-2001-80761).
JP-A-2001-80761 discusses a support shaft, to which a pickup unit has been attached, being supported by a side plate using a cantilever structure. To be more specific, with the paper supply apparatus disclosed in JP-A-2001-80761, the pickup unit is attached to a tip portion of the support shaft, which extends from a fixed guide (the side plate), and a paper supply roller is disposed on an end of the pickup unit so as to be capable of rotation. According to such a configuration, the surface of the paper is held down by the paper supply roller on the side where the fixed guide is located, and the paper is transported thus.
Incidentally, with paper supply apparatuses that include a paper supply roller that is rotationally driven while making contact with the surface of the paper on the side where the fixed guide is located, there are cases where the paper is transported in a state in which the paper is tilted relative to the transport direction. More specifically, as shown in FIGS. 19 and 20, a force that transports paper P is effected on one side of the paper P in a widthwise direction H by a paper supply roller 125 that is located on the side of a fixed guide 122 and that is rotationally driven while making contact with the surface of the paper P; however, there are cases where, when paper P that is highly elastic, such as heavy paper or the like, is transported, the side of the paper P on which the paper supply roller 125 is not located (that is, the side where a movable guide 103 is located) lifts away from a placement surface 121a while the paper P is being transported. The paper P lifting away in this manner causes a problem in that the paper P is transported by the paper supply apparatus 102 in a state in which the paper P is tilted relative to the transport direction.
One conceivable measure for avoiding such a problem is to provide an abutment member that abuts the surface of the paper, like the paper supply roller, on the side where the movable guide is located as well. It is also conceivable to bias the abutment member, which abutments the surface of the paper on the side where the movable guide is located, toward the placement surface using an elastic member, thereby effectively holding down the surface of the paper on the side where the movable guide is located using the abutment member.
However, when the abutment member is caused to abut the surface of the paper in the same manner in which the paper supply roller abuts the surface of the paper so as to suppress both sides of the paper from lifting off in the widthwise direction, there are cases where the abutment member, which is biased toward the placement surface, is damaged. In particular, it is necessary to bias the abutment member using an even stronger force when the paper is heavy paper or the like, and there are cases where the strength of the abutment member cannot be ensured.